A leading cause of major health issues ranging from blindness to kidney failure, diabetes often goes undetected in the early stages, which can thwart timely treatment and proper management.
The American Diabetes Association recommends screening for Type 2 diabetes beginning at age 45, with routine testing done at least every three years after that. Experts say those at greater risk of developing the condition, including people who are overweight or obese or who have a family history of diabetes, should talk with their doctors about being screened earlier. Several tests are generally recommended as options to detect diabetes or prediabetes, in which a person has slightly elevated blood-sugar levels, putting them at higher risk for developing diabetes. Those include a fasting plasma glucose, or blood glucose, test; an oral glucose tolerance test and a hemoglobin A1C test. (That’s in addition to a so-called casual plasma glucose test that can be done at any time, which may be used to test those with severe symptoms of diabetes.)
[See: The 12 Best Diets to Prevent and Manage Diabetes.]
Using A1C to Diagnose Diabetes
A1C provides information about a person’s average blood sugar, or blood glucose, levels for the past two to three months, and patients don’t need to fast, or drink a special sweet liquid, as required for the glucose tolerance test. It’s been used for decades in the management of diabetes, and has been recommended by the ADA since 2010 as a testing option to diagnose diabetes and prediabetes as well.
The higher your blood sugar levels, the more glucose sticks to the hemoglobin, or red blood cells, and the higher a person’s A1C will be, explains Dr. Robert Gabbay, chief medical officer at Joslin Diabetes Center, which is affiliated with Harvard Medical School, in Boston. “For the vast majority of patients, it’s a good measure,” he says. “But there are situations where it’s not accurate.” For example, some causes of anemia — which is characterized by a deficiency of hemoglobin — or advanced liver or kidney disease can affect the average 90-day lifespan of red blood cells, so that A1C no longer accurately reflects average blood sugar levels, Gabbay says. Older patients are more likely to suffer from some of the conditions, including blood disorders, that may undermine A1C accuracy as well, he says — something worth considering to ensure a diagnosis isn’t missed and blood sugars are properly controlled.
In addition, the presence of sickle cell trait — the most common so-called hemoglobin variant in the U.S. — was found in a study published in the Journal of the American Medical Association this month to lower the A1C values, which could affect diagnosis of prediabetes and diabetes.
About 8 to 10 percent of African-Americans have sickle cell trait, which is inherited from a parent with the sickle cell gene. Usually those with sickle cell trait don’t have any symptoms of sickle cell disease, a group of inherited red blood cell disorders. Despite that, the research found that A1C testing used in the study identified 40 percent fewer cases of prediabetes and 48 percent fewer cases of diabetes among African-American study participants with sickle cell trait, compared to African-American participants without the trait.
“What we found was a person with sickle cell trait, their A1C is about 0.3 percentage points lower than someone without sickle cell trait,” says lead study author Mary Lacy, a PhD candidate in epidemiology at Brown University School of Public Health in Providence, Rhode Island; that was the case even if the two people had the same blood-glucose values. “We would expect them to have a similar A1C if they have similar glucose. But we found that A1C was systematically lower in people with sickle cell trait.” At an A1C of 5.7 to 6.4, patients are diagnosed with prediabetes; an A1C of 6.5 or higher is needed to make a diagnosis of diabetes. Study participants with sickle cell trait were found on average to have an A1C of 5.72, compared with 6.01 for those without sickle cell trait.
[See: Got Diabetes? Why You Must Protect Your Feet.]
Relying on More Than One Test to Diagnose and Manage Diabetes
Researchers and outside experts note that more study is needed to determine what these findings might ultimately mean for patients or providers. But taking into account that A1C measures alone can sometimes miss a diagnosis of diabetes or prediabetes, clinicians say patients and providers should consider doing additional testing particularly when measures are borderline.
“I believe that the way to offset this potential problem with sickle cell trait is to combine A1C with another test, such as fasting glucose,” says Dr. Anne Sumner, a co-author on the research published in JAMA and chief of the Section on Ethnicity and Health at the National Institute of Diabetes, Digestive and Kidney Diseases.
Though many with sickle cell trait don’t know they have it, newborns are now screened for the trait; and those with a family history of sickle cell disease, or parents with a sickle gene (if known), can get a blood test to determine if they have sickle cell trait. In addition, experts recommend individuals with a family history of diabetes also consider talking with their doctor about whether doing additional testing is wise to make sure diabetes is properly diagnosed and managed — even if A1C results come back normal. “Do your due diligence to make sure that the blood sugars are not actually elevated,” says Dr. Matthew Sauder, a managing physician at Lancaster General Health Physicians Diabetes and Endocrinology, a general endocrinology group in Pennsylvania.
[See: 5 Ways to Reduce Your Risk of Developing Kidney Disease.]
All things considered, clinicians express relative confidence in the A1C measure for management and diagnosis of diabetes; Sauder says he uses the measure daily with his patients. “I check lots of A1Cs,” he says. “But we have to be aware that no one test can be a be-all, end-all test. We have to make sure we’re using all our data points, and not just rely on one single measurement.”
More from U.S. News
Do’s and Don’ts of Home Medical Devices
6 Healthy Foods Worth Splurging On
The 12 Best Diets to Prevent and Manage Diabetes
Imprecise A1C Readings May Hamper Diabetes Diagnosis or Management originally appeared on usnews.com
